Dynamo.



L. E UNDERWOOD. DYNAMO. APPLICATION FILED 11111.14, 1909. 1,003,955.Patented Sept. 19,1911.

2 SHEETS-SHEET 1.

L. E. UNDERWOOD.

DYNAMO. v APPLICATION FILED JAN. 14, 1909.

1,003,955. Patented Sept. 19,1911.

2 SHEETS-SHEET 2.

Withesses: Inventor:

%, Louis El Und rwood,

UNITED STATES PATENT OFFICE.

LOUIS IE. UNDERWOOD, OF LYNN, MASSACHUSETTS, ASSIGNOR TO GENERALELECTRIC COMPANY, A CORPORATION OE NEW YORK.

DYNAMO.

Specification of Letters Patent.

Patented Sept. 19, 1911.

Application filed January 14, 1909. Serial No. 472,245.

To all whom it may concern:

Be it known that I, LOUIS E. UNDERWOOD, a citizen of the United States,residing at Lynn, in the county of Essex, State of Massachusetts, haveinvented certain new and useful Improvements in Dynamos, of which thefollowing is a specification.

My invention relates to dynamos, and more particularly to dynamos whichare usedto produce a constant output, and con sists in a certainarrangementof the field and connections on the armature for producingthe required regulation. I accomplish this regulation by providing onthe armature connections which revolve with it and produce what may becalled a polyphase short-circuit upon the armature, and hencea fieldwhich will be angularly displaced from the initial exciting field. Iprovide commutator brushes which are so positioned as to produce anarmature reaction which will be in a direction parallel to and opposingthat of the initial exciting field. I may also, if I so desire, providea field displaced from the initial exciting field, in addition to it,the field produced by the polyphase short-circuit on the armature, andthe field due to the armature reaction, and whose position dependsuponthat of the commutator brushes. The intensities and the resultants ofthese fields may be so proportioned that a dynamo built, in accordancewith my invention, may be made to give a constant output, orsubstantially a constant current independent of the speed at which thearmature revolves.

For a further understanding of my invention, reference may be had to theaccompanying drawings, where Figure 1 shows diagrammatically a dynamo inaccordance with my invention; Fig. 2 shows a vector diagram of thefields for the same; Fig. 3 shows a modification ofFig. 1; Fig. 4 is avector diagram for this modification; Fig. 5 is another modification ofmy invention; and Fig. 6 is a vector diagram showing the relation of thefields described in Fig. 5.

Referring first to Fig. l, I have shown a frame, to which are attachedpoles 2, 3, e and 5. Revolving within these poles I have showndiagrammatically an armature 6, consisting of a winding .7 and acommutator 8. 9 are the commutator brushes. The armature is shownsymbolically, as a Grammearmature, and the commutator is shownexillustration; but it will be obvious that any of the well-known formsof winding may be used, and that while I have shown my invention asapplied to a bipolar machine, this is only for the same purpose ofconvenience in illustration, as my invention may be applied tomultipolar machines equally well. At points 10, which are shownasdisplaced from each other 120 electrical degrees, the armature isshort-circuited through connections 10 which produce a polyphaseshort-circuit upon it. Inserted in these connections are shownimpedances 11, but if desired, these impedances may be omitted. IVhilefor the purposes of illustration a three-phase short-circuit is shown onthe armature, any polyphase short-circuit may be used if desired. Thecommutator brushes 9 are shown as feeding translating devices 12. Poles2 and 3 produce a field which is called for the purpose of conveniencethe initial field, and these poles are excited by a shunt winding inseries with which is an adjustable resistance 13. Poles 4 and 5 areexcited by the series winding and are displaced 90 degrees from theinitial field. The commutator brushes 9 are shown in a position toproduce an armature reaction, which shall be in line with the fieldproduced by the shunt winding upon the poles 2 and 3. The poles 2 and 3are shown as having a small section cut out over the brushes for thepurpose of commutation, but it is obvious that this is not essential foroperation.

Referring now to Fig. 2, if the direction of the initial field of poles2 and 3 be represented by the arrow 15, the voltage induced in thearmature this field, which is at right angles to the direction of thefield, will be in the direction of the arrow 14 If the current flowingthrough the short-circuiting connections were in phase with the voltageinduced in the armature by the initial field, this current, orrather,the direction of its magneto-motive force, will also be in the directionindicated by 1& If, on the other hand, the circuit formed by thearmature winding and short-circuiting connections were wholly inductiveinstead of non-inductive, so that the current in these connections.lagged 90 behind the induced voltage, the current in these connectionsand its magneto-motive force would be substantially in.

- into two components 1 1 and 1&

short-clrcuiting connections and the impedances therein is partlyinductive and partly non-inductive, the current in these connec-v tionsand the direction of its magneto-motive force may be represented by thearrow 14. This magneto-motive force may be resolved Component 14: isdisplaced 90 from the initial field and, consequently, from the line ofthe commutator brushes, and this component is the cross field whichinduces the voltage between the commutator brushes. The field producedby poles 4 and 5 is shown by vector 16, and the direction of this fieldis such as to oppose the component 1 1 of the polyphase short-circuitfield 14. The other component of the vector 14, 14 opposes the directionof the initial field '15. The armature reaction is shown by vector 17opposing the initial field 15, but being in the same direction as thecomponent of the polyphas short-circuit field 14 The action of themachine for producing a constant output will then be as' follows If themachine is feeding an external circuit under such conditions that thevectorial relation shown by Fig. 2 exists, when the resistance of thecircuit is cut down, the current will tend to increase. This producestwo effects, both of which decrease the voltage at the commutatorbrushes. In the first place the armature reaction in the line of thecommutator brushes, represented in Fig.

2 by 17, increases, thereby weakening the initial .field and,consequently, reducing the current produced in the short-circuitedconnections and its magneto-motive force indicated by the arrow 14.'Furthermore, the increased current in the coils on poles 4 and 5increases the. magnetomotive force in these poles, indicated by 16, Fig.2', and

this increased magneto-motive force still further weakens the component14 of the cross field which induces the voltage between the commutatorbrushes. Thus by proper proportioning of parts a machine ofsubstantially constant output can be produced. Also by a properproportioning of parts a machine of an approximately constant currentindependentof the speed and the load maybe produced. The polyphasecurrent flowing in the polyphase short-circuit in the armature isdependent upon the impedence of the armature. When the speed ofrevolution of the armature increases, the reactanee in' the polyphaseshort-circuit also increases. The result is that the polyphase field ispractically'independent of the-speed. If the initial field is given aconstant excitation and the armature reaction is a strong one,-thecurrent will be substantially constant and independent of the load andthe speed, for we may decrease the resultant initial and cross Brushes 9are consider vector 14 as approximately constant, vector 15 as constant.Vectors 16 and 17 would tend to increase for an increase of speed, butany such increase would tend to fields. Thus the current will beapproximately constant.

Referring now to Fig. 3, I have shown a modification of Fig. 1. Thismodification consists in omitting the series winding upon the poles 4and 5. The vector diagram for this modification is shown in Fig. 4, andit is substantially similar to that of Fig. 2, with the exception thatvector 16 is omitted. The poles 4 and 5 are used in order to assist theflux produced by the polyphase shortcircuit.

In Fig. 5 I have shown a still further modification of Fig. 1. Themodification consists in omitting poles 4 and 5 and em- 8 ployingauxiliary poles 4 and 5 which are displaced at an angle less than 90degrees from the poles producing the initial field. displaced so as toproduce an armature reaction in line with the poles R41 and 5 and thesepoles are used so-as to decrease the reluctance in the path of the fluxdue to the armature reaction. Fig. 6 shows a vector diagram for thisarrangement, where 17 is the field produced by the armature reaction.This field may be resolved into two components 17 and 17 17 tending tooppose the .oomponent 14 of the field due to the polyphaseshort-circuit, and 17 tending to oppose the initial field. It will beseen that the action of this modification of my invention is similar tothe action of the embodiment shown in Fig. 1, as the shifting of thebrushes to produce an armature reaction displaced in line from the lineof the initial field merely produces a vector diagram similar to thatshown in Fig. 2, the component 17 of the armature reaction being similarto component 16 due to the series field. When the armature is short- 1circuited, or the resistance is greatly decreased, the armature reaction17 will indrease, and thus each of its components will increase, and theoutput will be substantially constant. .1

While I have shown certain forms or arrangements of embodiments of myinvention I do not limit myself to these forms or arrangements, but seekin the appended claims to cover all are within the scope of which willbe obvious to art.

What I claim as new and desire to secure my invention, and those skilledin the by Letters Patent of the United States, is, 1

1. In an electric machine, the combination of field coils andconnections for producing a unidirectional initial field, an armaturehaving a commutator revolving within the field, with plurality ofconnec- 1 forms and arrangements which 1 tions on the armature windingshort-circuiting the winding and forming paths for the current inducedin the armature which produces in the armature a field angularlydisplaced from the initial field.

2. In an electric machine, the combina I tion of field coils andconnections for proconnections therefor for producing. in said ducingv aunidirectional initial field, an armature havin a commutator revolvingwithin the fie d, commutator brushes and connections feeding a circuit,and means revolving with the armature producing a polyphase shortcircuiton the armature.

3. In an electric machine, the combination of field coils andconnections for producing a unidirectional initial field, an armaturehaving a commutator revolving within the field, commutator brushesplaced to produce an armature reaction in a direction parallel to theinitial field and connections feeding a circuit, and means revolvingwith the armature producing a three-phase short-circuit on the armature.

4:. In an electric machine, the combination of field coils andconnections for producing a unidirectional initial field, an armaturehaving a commutator revolving within the field, commutator brushes andconnections feeding a circuit, and impedances and connections thereforforming a polyphase short-circuit on the armature.

5. In an electric machine, the combination of a set of field poles,field coils and poles a unidirectional initial fi'eld; a second set offield poles angularly displaced therefrom, an armature having acommutator revolving Within the field poles, and connections on thearmature revolving with it, and forming a path for the current inducedin the armature which produces in the armature a field angularlydisplaced from the initial field. I Q

6. In an electric machine, the combination of a set of field poles,field coils and connections for producing in said poles a unidirectionalinitial field, a second set of field poles angularly displacedtherefrom, an armature having a commutator revolving Within the fieldpoles, and means producing a polyphase short-circuit on it.

tions for producing in said poles a unidirectional initial field, asecond set of field poles angularly displaced therefrom, an armaturehaving .a commutator revolving within the field poles, and meansrevolving with the armature'producing a three-phase short-circuit on it.

8. In an electric machine, the combination or a set of field poles,coils and connections for producing in said poles an initial field, asecond set of field poles displaced ninety degrees therefrom, anarmature having a commutator revolving Within the field poles,commutator brushes placed to produce an armature reaction in a directionparallel to that of the initial field, and connections revolving withthe armature producing a polyphase short-circuit on it.

9. In an electric machine, the combination of a set of field poles, ashunt winding thereon and connections for producing in said poles aninitial field, a second set of field poles displaced ninety degreestherefrom, an armature having a commutator Irevolving within the fieldpoles, commutator brushes placed to produce an armature reaction in adirection parallel to that of the initial field, and connectionsrevolving with the armature producing a polyphase shortcircuit on it. v

10. In an electric machine, the combination of a set of field poles, ashunt Winding thereon and connections for producing in said poles aninitial field, a second set of field poles displaced ninety degrees,therefrom, an armature having a commutator revolving within the fieldpoles, commutator brushes placed to produce an armature reaction in adirection opposed to that of the initial field, a series Winding on thesecond set of field poles, and connections revolving with the armatureproducing a three-phase short-circuit upon it.

In witness whereof, I have hereunto set my hand this twelfth day ofJanuary, 1909.

LOUIS E. UNDERWOOD.

Witnesses:

JOHN A. MOMANUS, Jr., CHARLES A. BARNARD.

